Average norms of polynomials

In this paper we study the average ${\text{NL}}_{2\alpha }$-norm over $T$-polynomials, where $\alpha$ is a positive integer. More precisely, we present an explicit formula for the average ${\text{NL}}_{2\alpha }$-norm over all the polynomials of degree exactly $n$ with coefficients in $T$, where $T$ is a finite set of complex numbers, $\alpha$ is a positive integer, and $n\ge 0$. In particular, we give a complete answer for the cases of Littlewood polynomials and polynomials of a given height. As a consequence, we derive all the previously known results for this kind of problems, as well as many new results.